Hi sb and welcome to the forum
Yes it is possible - providing you obtain your Supervisor's express permission (I suggest in writing) and can find a finance companu willing to lend to someone in an IVA. Storm, one of the forum's regular posters, works in the industry and may be able to suggest a suitable lender.
You will also need to ensure that the new payments do not affect your ability to continue with your set monthly contributions, or otherwise a formal variation of the terms might be necessary.
Regards, Melanie Giles, Insolvency Practitioner for over 20 years.
For further details contact me at
http://www.melaniegiles.com and view my IVA blog at:
http://melaniegiles.blogs.iva.co.uk